This disclosure relates to the subject matter contained in Japanese Patent Application No.2001-287225 filed on Sep. 20, 2001, which is incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to a hollow golf club head made of metal, and particularly relates to a golf club head having a wood type shape or a shape close to the wood type shape.
2. Description of the Related Art
Hollow golf club heads made of metal are used widely as wood type golf club heads such as drivers or fairway woods. Generally, as shown in FIG. 6, a hollow wood type golf club head 1xe2x80x2 has a face portion 2 for hitting a ball, a crown portion 3 forming the top surface portion of the golf club head, a sole portion 4 forming the bottom surface portion of the golf club head, toe-side, back-side and heel-side side portions 5a, 5b and 5c forming the toe-side, back-side and heel-side side surface portions of the golf club head respectively, and a hosel portion 6. A shaft 7 is inserted into the hosel portion 6 of the golf club head 1xe2x80x2, and fixed thereto by a bonding agent or the like. Incidentally, recently, a lot of golf club heads called utility clubs have come onto the market. As a kind of such utility golf club head, various golf club heads resembling the wood type golf club head (that is, having a face portion, a sole portion, respective side portions and a crown portion) have also come onto the market.
As metal forming such a hollow golf club head, aluminum alloys, stainless steel, or titanium alloys are used. In recent years, titanium alloys are especially used widely.
In order to increase a carry of a shot with a hollow golf club head made of metal, development has been made while attention has been paid to the fact that the repulsion of a ball is increased by use of the bending of a face surface so as to hit the ball farther. However, for a golfer who has a low head speed, the deformation of the face surface in a golf club head of this type is insufficient so that the effect to increase the initial speed of the ball is reduced. In addition, the ball cannot be launched high. Thus, the carry may be not increased.
It is an object of the invention to provide a golf club head in which, even if a golfer who has a low head speed uses the golf club head, the launch angle is increased so that the carry can be increased consequently.
A hollow golf club head according to the invention is made of metal. The golf club has a face portion, a sole portion, a toe-side side portion, a heel-side side portion, a back-side side portion, a crown portion, and a hosel portion. A plurality of grooves are defined in the crown portion to extend from the toe-side side portion toward the heel-side side portion.
In the golf club head configured thus according to the invention, the crown portion is easily bent at the time of impact by the operation of the grooves provided in the crown portion. Accordingly, even if a beginner or a powerless player who has a low head speed uses the golf club head, the initial speed of a ball increases while the backspin rate increases and the launch angle also increases. Thus, these operations are superposed on one another so as to increase the carry.
The grooves in the crown portion may extend substantially straight lines from the toe-side side portion toward the heel-side side portion, or may be formed in curved lines and be bent to bulge toward the back-side side portion.
According to the invention, it is preferable that the highest portion of the crown portion excluding the hosel portion is located between two of the grooves. With such a configuration, the stress applied to the crown portion at the time of impact is dispersed over a wide region of the crown portion so that the crown portion as a whole is bent. Thus, large repulsive force can be generated.
According to the invention, ribs may be provided in the sole portion so as to extend from the face portion toward the back-side side portion, or salient portions may be provided on the bottom surface of the sole portion so as to angulate and extend from the face portion toward the back-side side portion, so that the deformation of the sole portion at the time of impact is suppressed. Thus, the stress is concentrated on the crown portion at the time of impact so that the crown portion becomes easier to bend. As a result, the carry increases further.
It is preferable to apply the invention to a large-sized golf club head having a volume over 250 cc, especially over 300 cc, more especially over 350 cc. An example of such a golf club head is a driver. However, the invention is also applicable to a fairway wood, a utility golf club head resembling wood type one, and the like.